/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: XStringForFSB.java,v 1.2.4.2 2005/09/14 20:46:27 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.objects;

import com.sun.org.apache.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xml.internal.utils.FastStringBuffer;
import com.sun.org.apache.xml.internal.utils.XMLCharacterRecognizer;
import com.sun.org.apache.xml.internal.utils.XMLString;
import com.sun.org.apache.xml.internal.utils.XMLStringFactory;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;

/**
 * This class will wrap a FastStringBuffer and allow for
 */
public class XStringForFSB extends XString {
    static final long serialVersionUID = -1533039186550674548L;

    /** The start position in the fsb. */
    int m_start;

    /** The length of the string. */
    int m_length;

    /** If the str() function is called, the string will be cached here. */
    protected String m_strCache = null;

    /** cached hash code */
    protected int m_hash = 0;

    /**
     * Construct a XNodeSet object.
     *
     * @param val FastStringBuffer object this will wrap, must be non-null.
     * @param start The start position in the array.
     * @param length The number of characters to read from the array.
     */
    public XStringForFSB(FastStringBuffer val, int start, int length) {

        super(val);

        m_start = start;
        m_length = length;

        if (null == val)
            throw new IllegalArgumentException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_FASTSTRINGBUFFER_CANNOT_BE_NULL, null));
    }

    /**
     * Construct a XNodeSet object.
     *
     * @param val String object this will wrap.
     */
    private XStringForFSB(String val) {

        super(val);

        throw new IllegalArgumentException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_FSB_CANNOT_TAKE_STRING, null)); // "XStringForFSB can not take a string for an argument!");
    }

    /**
     * Cast result object to a string.
     *
     * @return The string this wraps or the empty string if null
     */
    public FastStringBuffer fsb() {
        return ((FastStringBuffer) m_obj);
    }

    /**
     * Cast result object to a string.
     *
     * @return The string this wraps or the empty string if null
     */
    public void appendToFsb(com.sun.org.apache.xml.internal.utils.FastStringBuffer fsb) {
        // %OPT% !!! FSB has to be updated to take partial fsb's for append.
        fsb.append(str());
    }

    /**
     * Tell if this object contains a java String object.
     *
     * @return true if this XMLString can return a string without creating one.
     */
    public boolean hasString() {
        return (null != m_strCache);
    }

    //  /** NEEDSDOC Field strCount */
    //  public static int strCount = 0;
    //
    //  /** NEEDSDOC Field xtable */
    //  static java.util.Hashtable xtable = new java.util.Hashtable();

    /**
     * Since this object is incomplete without the length and the offset, we
     * have to convert to a string when this function is called.
     *
     * @return The java String representation of this object.
     */
    public Object object() {
        return str();
    }

    /**
     * Cast result object to a string.
     *
     * @return The string this wraps or the empty string if null
     */
    public String str() {

        if (null == m_strCache) {
            m_strCache = fsb().getString(m_start, m_length);

            //      strCount++;
            //
            //      RuntimeException e = new RuntimeException("Bad!  Bad!");
            //      java.io.CharArrayWriter writer = new java.io.CharArrayWriter();
            //      java.io.PrintWriter pw = new java.io.PrintWriter(writer);
            //
            //      e.printStackTrace(pw);
            //
            //      String str = writer.toString();
            //
            //      str = str.substring(0, 600);
            //
            //      if (null == xtable.get(str))
            //      {
            //        xtable.put(str, str);
            //        System.out.println(str);
            //      }
            //      System.out.println("strCount: " + strCount);

            //      throw e;
            //      e.printStackTrace();
            // System.exit(-1);
        }

        return m_strCache;
    }

    /**
     * Directly call the
     * characters method on the passed ContentHandler for the
     * string-value. Multiple calls to the
     * ContentHandler's characters methods may well occur for a single call to
     * this method.
     *
     * @param ch A non-null reference to a ContentHandler.
     *
     * @throws org.xml.sax.SAXException
     */
    public void dispatchCharactersEvents(org.xml.sax.ContentHandler ch) throws org.xml.sax.SAXException {
        fsb().sendSAXcharacters(ch, m_start, m_length);
    }

    /**
     * Directly call the
     * comment method on the passed LexicalHandler for the
     * string-value.
     *
     * @param lh A non-null reference to a LexicalHandler.
     *
     * @throws org.xml.sax.SAXException
     */
    public void dispatchAsComment(org.xml.sax.ext.LexicalHandler lh) throws org.xml.sax.SAXException {
        fsb().sendSAXComment(lh, m_start, m_length);
    }

    /**
     * Returns the length of this string.
     *
     * @return  the length of the sequence of characters represented by this
     *          object.
     */
    public int length() {
        return m_length;
    }

    /**
     * Returns the character at the specified index. An index ranges
     * from <code>0</code> to <code>length() - 1</code>. The first character
     * of the sequence is at index <code>0</code>, the next at index
     * <code>1</code>, and so on, as for array indexing.
     *
     * @param      index   the index of the character.
     * @return     the character at the specified index of this string.
     *             The first character is at index <code>0</code>.
     * @exception  IndexOutOfBoundsException  if the <code>index</code>
     *             argument is negative or not less than the length of this
     *             string.
     */
    public char charAt(int index) {
        return fsb().charAt(m_start + index);
    }

    /**
     * Copies characters from this string into the destination character
     * array.
     *
     * @param      srcBegin   index of the first character in the string
     *                        to copy.
     * @param      srcEnd     index after the last character in the string
     *                        to copy.
     * @param      dst        the destination array.
     * @param      dstBegin   the start offset in the destination array.
     * @exception IndexOutOfBoundsException If any of the following
     *            is true:
     *            <ul><li><code>srcBegin</code> is negative.
     *            <li><code>srcBegin</code> is greater than <code>srcEnd</code>
     *            <li><code>srcEnd</code> is greater than the length of this
     *                string
     *            <li><code>dstBegin</code> is negative
     *            <li><code>dstBegin+(srcEnd-srcBegin)</code> is larger than
     *                <code>dst.length</code></ul>
     * @exception NullPointerException if <code>dst</code> is <code>null</code>
     */
    public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {

        // %OPT% Need to call this on FSB when it is implemented.
        // %UNTESTED% (I don't think anyone calls this yet?)
        int n = srcEnd - srcBegin;

        if (n > m_length)
            n = m_length;

        if (n > (dst.length - dstBegin))
            n = (dst.length - dstBegin);

        int end = srcBegin + m_start + n;
        int d = dstBegin;
        FastStringBuffer fsb = fsb();

        for (int i = srcBegin + m_start; i < end; i++) {
            dst[d++] = fsb.charAt(i);
        }
    }

    /**
     * Compares this string to the specified object.
     * The result is <code>true</code> if and only if the argument is not
     * <code>null</code> and is a <code>String</code> object that represents
     * the same sequence of characters as this object.
     *
     * @param   obj2       the object to compare this <code>String</code>
     *                     against.
     *
     * @return  <code>true</code> if the <code>String </code>are equal;
     *          <code>false</code> otherwise.
     * @see     java.lang.String#compareTo(java.lang.String)
     * @see     java.lang.String#equalsIgnoreCase(java.lang.String)
     */
    public boolean equals(XMLString obj2) {

        if (this == obj2) {
            return true;
        }

        int n = m_length;

        if (n == obj2.length()) {
            FastStringBuffer fsb = fsb();
            int i = m_start;
            int j = 0;

            while (n-- != 0) {
                if (fsb.charAt(i) != obj2.charAt(j)) {
                    return false;
                }

                i++;
                j++;
            }

            return true;
        }

        return false;
    }

    /**
     * Tell if two objects are functionally equal.
     *
     * @param obj2 Object to compare this to
     *
     * @return true if the two objects are equal
     *
     * @throws javax.xml.transform.TransformerException
     */
    public boolean equals(XObject obj2) {

        if (this == obj2) {
            return true;
        }
        if (obj2.getType() == XObject.CLASS_NUMBER)
            return obj2.equals(this);

        String str = obj2.str();
        int n = m_length;

        if (n == str.length()) {
            FastStringBuffer fsb = fsb();
            int i = m_start;
            int j = 0;

            while (n-- != 0) {
                if (fsb.charAt(i) != str.charAt(j)) {
                    return false;
                }

                i++;
                j++;
            }

            return true;
        }

        return false;
    }

    /**
     * Tell if two objects are functionally equal.
     *
     * @param anotherString Object to compare this to
     *
     * @return true if the two objects are equal
     *
     * @throws javax.xml.transform.TransformerException
     */
    public boolean equals(String anotherString) {

        int n = m_length;

        if (n == anotherString.length()) {
            FastStringBuffer fsb = fsb();
            int i = m_start;
            int j = 0;

            while (n-- != 0) {
                if (fsb.charAt(i) != anotherString.charAt(j)) {
                    return false;
                }

                i++;
                j++;
            }

            return true;
        }

        return false;
    }

    /**
     * Compares this string to the specified object.
     * The result is <code>true</code> if and only if the argument is not
     * <code>null</code> and is a <code>String</code> object that represents
     * the same sequence of characters as this object.
     *
     * @param   obj2       the object to compare this <code>String</code>
     *                     against.
     *
     * @return  <code>true</code> if the <code>String </code>are equal;
     *          <code>false</code> otherwise.
     * @see     java.lang.String#compareTo(java.lang.String)
     * @see     java.lang.String#equalsIgnoreCase(java.lang.String)
     */
    public boolean equals(Object obj2) {

        if (null == obj2)
            return false;

        if (obj2 instanceof XNumber)
            return obj2.equals(this);

        // In order to handle the 'all' semantics of
        // nodeset comparisons, we always call the
        // nodeset function.
        else if (obj2 instanceof XNodeSet)
            return obj2.equals(this);
        else if (obj2 instanceof XStringForFSB)
            return equals((XMLString) obj2);
        else
            return equals(obj2.toString());
    }

    /**
     * Compares this <code>String</code> to another <code>String</code>,
     * ignoring case considerations.  Two strings are considered equal
     * ignoring case if they are of the same length, and corresponding
     * characters in the two strings are equal ignoring case.
     *
     * @param   anotherString   the <code>String</code> to compare this
     *                          <code>String</code> against.
     * @return  <code>true</code> if the argument is not <code>null</code>
     *          and the <code>String</code>s are equal,
     *          ignoring case; <code>false</code> otherwise.
     * @see     #equals(Object)
     * @see     java.lang.Character#toLowerCase(char)
     * @see java.lang.Character#toUpperCase(char)
     */
    public boolean equalsIgnoreCase(String anotherString) {
        return (m_length == anotherString.length()) ? str().equalsIgnoreCase(anotherString) : false;
    }

    /**
     * Compares two strings lexicographically.
     *
     * @param   xstr   the <code>String</code> to be compared.
     *
     * @return  the value <code>0</code> if the argument string is equal to
     *          this string; a value less than <code>0</code> if this string
     *          is lexicographically less than the string argument; and a
     *          value greater than <code>0</code> if this string is
     *          lexicographically greater than the string argument.
     * @exception java.lang.NullPointerException if <code>anotherString</code>
     *          is <code>null</code>.
     */
    public int compareTo(XMLString xstr) {

        int len1 = m_length;
        int len2 = xstr.length();
        int n = Math.min(len1, len2);
        FastStringBuffer fsb = fsb();
        int i = m_start;
        int j = 0;

        while (n-- != 0) {
            char c1 = fsb.charAt(i);
            char c2 = xstr.charAt(j);

            if (c1 != c2) {
                return c1 - c2;
            }

            i++;
            j++;
        }

        return len1 - len2;
    }

    /**
     * Compares two strings lexicographically, ignoring case considerations.
     * This method returns an integer whose sign is that of
     * <code>this.toUpperCase().toLowerCase().compareTo(
     * str.toUpperCase().toLowerCase())</code>.
     * <p>
     * Note that this method does <em>not</em> take locale into account,
     * and will result in an unsatisfactory ordering for certain locales.
     * The java.text package provides <em>collators</em> to allow
     * locale-sensitive ordering.
     *
     * @param   xstr   the <code>String</code> to be compared.
     *
     * @return  a negative integer, zero, or a positive integer as the
     *          the specified String is greater than, equal to, or less
     *          than this String, ignoring case considerations.
     * @see     java.text.Collator#compare(String, String)
     * @since   1.2
     */
    public int compareToIgnoreCase(XMLString xstr) {

        int len1 = m_length;
        int len2 = xstr.length();
        int n = Math.min(len1, len2);
        FastStringBuffer fsb = fsb();
        int i = m_start;
        int j = 0;

        while (n-- != 0) {
            char c1 = Character.toLowerCase(fsb.charAt(i));
            char c2 = Character.toLowerCase(xstr.charAt(j));

            if (c1 != c2) {
                return c1 - c2;
            }

            i++;
            j++;
        }

        return len1 - len2;
    }

    /**
     * Returns a hashcode for this string. The hashcode for a
     * <code>String</code> object is computed as
     * <blockquote><pre>
     * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
     * </pre></blockquote>
     * using <code>int</code> arithmetic, where <code>s[i]</code> is the
     * <i>i</i>th character of the string, <code>n</code> is the length of
     * the string, and <code>^</code> indicates exponentiation.
     * (The hash value of the empty string is zero.)
     *
     * @return  a hash code value for this object.
     */
    public int hashCode() {
        // Commenting this out because in JDK1.1.8 and VJ++
        // we don't match XMLStrings. Defaulting to the super
        // causes us to create a string, but at this point
        // this only seems to get called in key processing.
        // Maybe we can live with it?

        /*
            int h = m_hash;
        
            if (h == 0)
            {
              int off = m_start;
              int len = m_length;
              FastStringBuffer fsb = fsb();
        
              for (int i = 0; i < len; i++)
              {
                h = 31 * h + fsb.charAt(off);
        
                off++;
              }
        
              m_hash = h;
            }
            */

        return super.hashCode(); // h;
    }

    /**
     * Tests if this string starts with the specified prefix beginning
     * a specified index.
     *
     * @param   prefix    the prefix.
     * @param   toffset   where to begin looking in the string.
     * @return  <code>true</code> if the character sequence represented by the
     *          argument is a prefix of the substring of this object starting
     *          at index <code>toffset</code>; <code>false</code> otherwise.
     *          The result is <code>false</code> if <code>toffset</code> is
     *          negative or greater than the length of this
     *          <code>String</code> object; otherwise the result is the same
     *          as the result of the expression
     *          <pre>
     *          this.subString(toffset).startsWith(prefix)
     *          </pre>
     * @exception java.lang.NullPointerException if <code>prefix</code> is
     *          <code>null</code>.
     */
    public boolean startsWith(XMLString prefix, int toffset) {

        FastStringBuffer fsb = fsb();
        int to = m_start + toffset;
        int tlim = m_start + m_length;
        int po = 0;
        int pc = prefix.length();

        // Note: toffset might be near -1>>>1.
        if ((toffset < 0) || (toffset > m_length - pc)) {
            return false;
        }

        while (--pc >= 0) {
            if (fsb.charAt(to) != prefix.charAt(po)) {
                return false;
            }

            to++;
            po++;
        }

        return true;
    }

    /**
     * Tests if this string starts with the specified prefix.
     *
     * @param   prefix   the prefix.
     * @return  <code>true</code> if the character sequence represented by the
     *          argument is a prefix of the character sequence represented by
     *          this string; <code>false</code> otherwise.
     *          Note also that <code>true</code> will be returned if the
     *          argument is an empty string or is equal to this
     *          <code>String</code> object as determined by the
     *          {@link #equals(Object)} method.
     * @exception java.lang.NullPointerException if <code>prefix</code> is
     *          <code>null</code>.
     * @since   JDK1. 0
     */
    public boolean startsWith(XMLString prefix) {
        return startsWith(prefix, 0);
    }

    /**
     * Returns the index within this string of the first occurrence of the
     * specified character. If a character with value <code>ch</code> occurs
     * in the character sequence represented by this <code>String</code>
     * object, then the index of the first such occurrence is returned --
     * that is, the smallest value <i>k</i> such that:
     * <blockquote><pre>
     * this.charAt(<i>k</i>) == ch
     * </pre></blockquote>
     * is <code>true</code>. If no such character occurs in this string,
     * then <code>-1</code> is returned.
     *
     * @param   ch   a character.
     * @return  the index of the first occurrence of the character in the
     *          character sequence represented by this object, or
     *          <code>-1</code> if the character does not occur.
     */
    public int indexOf(int ch) {
        return indexOf(ch, 0);
    }

    /**
     * Returns the index within this string of the first occurrence of the
     * specified character, starting the search at the specified index.
     * <p>
     * If a character with value <code>ch</code> occurs in the character
     * sequence represented by this <code>String</code> object at an index
     * no smaller than <code>fromIndex</code>, then the index of the first
     * such occurrence is returned--that is, the smallest value <i>k</i>
     * such that:
     * <blockquote><pre>
     * (this.charAt(<i>k</i>) == ch) && (<i>k</i> >= fromIndex)
     * </pre></blockquote>
     * is true. If no such character occurs in this string at or after
     * position <code>fromIndex</code>, then <code>-1</code> is returned.
     * <p>
     * There is no restriction on the value of <code>fromIndex</code>. If it
     * is negative, it has the same effect as if it were zero: this entire
     * string may be searched. If it is greater than the length of this
     * string, it has the same effect as if it were equal to the length of
     * this string: <code>-1</code> is returned.
     *
     * @param   ch          a character.
     * @param   fromIndex   the index to start the search from.
     * @return  the index of the first occurrence of the character in the
     *          character sequence represented by this object that is greater
     *          than or equal to <code>fromIndex</code>, or <code>-1</code>
     *          if the character does not occur.
     */
    public int indexOf(int ch, int fromIndex) {

        int max = m_start + m_length;
        FastStringBuffer fsb = fsb();

        if (fromIndex < 0) {
            fromIndex = 0;
        } else if (fromIndex >= m_length) {

            // Note: fromIndex might be near -1>>>1.
            return -1;
        }

        for (int i = m_start + fromIndex; i < max; i++) {
            if (fsb.charAt(i) == ch) {
                return i - m_start;
            }
        }

        return -1;
    }

    /**
     * Returns a new string that is a substring of this string. The
     * substring begins with the character at the specified index and
     * extends to the end of this string. <p>
     * Examples:
     * <blockquote><pre>
     * "unhappy".substring(2) returns "happy"
     * "Harbison".substring(3) returns "bison"
     * "emptiness".substring(9) returns "" (an empty string)
     * </pre></blockquote>
     *
     * @param      beginIndex   the beginning index, inclusive.
     * @return     the specified substring.
     * @exception  IndexOutOfBoundsException  if
     *             <code>beginIndex</code> is negative or larger than the
     *             length of this <code>String</code> object.
     */
    public XMLString substring(int beginIndex) {

        int len = m_length - beginIndex;

        if (len <= 0)
            return XString.EMPTYSTRING;
        else {
            int start = m_start + beginIndex;

            return new XStringForFSB(fsb(), start, len);
        }
    }

    /**
     * Returns a new string that is a substring of this string. The
     * substring begins at the specified <code>beginIndex</code> and
     * extends to the character at index <code>endIndex - 1</code>.
     * Thus the length of the substring is <code>endIndex-beginIndex</code>.
     *
     * @param      beginIndex   the beginning index, inclusive.
     * @param      endIndex     the ending index, exclusive.
     * @return     the specified substring.
     * @exception  IndexOutOfBoundsException  if the
     *             <code>beginIndex</code> is negative, or
     *             <code>endIndex</code> is larger than the length of
     *             this <code>String</code> object, or
     *             <code>beginIndex</code> is larger than
     *             <code>endIndex</code>.
     */
    public XMLString substring(int beginIndex, int endIndex) {

        int len = endIndex - beginIndex;

        if (len > m_length)
            len = m_length;

        if (len <= 0)
            return XString.EMPTYSTRING;
        else {
            int start = m_start + beginIndex;

            return new XStringForFSB(fsb(), start, len);
        }
    }

    /**
     * Concatenates the specified string to the end of this string.
     *
     * @param   str   the <code>String</code> that is concatenated to the end
     *                of this <code>String</code>.
     * @return  a string that represents the concatenation of this object's
     *          characters followed by the string argument's characters.
     * @exception java.lang.NullPointerException if <code>str</code> is
     *          <code>null</code>.
     */
    public XMLString concat(String str) {

        // %OPT% Make an FSB here?
        return new XString(str().concat(str));
    }

    /**
     * Removes white space from both ends of this string.
     *
     * @return  this string, with white space removed from the front and end.
     */
    public XMLString trim() {
        return fixWhiteSpace(true, true, false);
    }

    /**
     * Returns whether the specified <var>ch</var> conforms to the XML 1.0 definition
     * of whitespace.  Refer to <A href="http://www.w3.org/TR/1998/REC-xml-19980210#NT-S">
     * the definition of <CODE>S</CODE></A> for details.
     * @param   ch      Character to check as XML whitespace.
     * @return          =true if <var>ch</var> is XML whitespace; otherwise =false.
     */
    private static boolean isSpace(char ch) {
        return XMLCharacterRecognizer.isWhiteSpace(ch); // Take the easy way out for now.
    }

    /**
     * Conditionally trim all leading and trailing whitespace in the specified String.
     * All strings of white space are
     * replaced by a single space character (#x20), except spaces after punctuation which
     * receive double spaces if doublePunctuationSpaces is true.
     * This function may be useful to a formatter, but to get first class
     * results, the formatter should probably do it's own white space handling
     * based on the semantics of the formatting object.
     *
     * @param   trimHead    Trim leading whitespace?
     * @param   trimTail    Trim trailing whitespace?
     * @param   doublePunctuationSpaces    Use double spaces for punctuation?
     * @return              The trimmed string.
     */
    public XMLString fixWhiteSpace(boolean trimHead, boolean trimTail, boolean doublePunctuationSpaces) {

        int end = m_length + m_start;
        char[] buf = new char[m_length];
        FastStringBuffer fsb = fsb();
        boolean edit = false;

        /* replace S to ' '. and ' '+ -> single ' '. */
        int d = 0;
        boolean pres = false;

        for (int s = m_start; s < end; s++) {
            char c = fsb.charAt(s);

            if (isSpace(c)) {
                if (!pres) {
                    if (' ' != c) {
                        edit = true;
                    }

                    buf[d++] = ' ';

                    if (doublePunctuationSpaces && (d != 0)) {
                        char prevChar = buf[d - 1];

                        if (!((prevChar == '.') || (prevChar == '!') || (prevChar == '?'))) {
                            pres = true;
                        }
                    } else {
                        pres = true;
                    }
                } else {
                    edit = true;
                    pres = true;
                }
            } else {
                buf[d++] = c;
                pres = false;
            }
        }

        if (trimTail && 1 <= d && ' ' == buf[d - 1]) {
            edit = true;

            d--;
        }

        int start = 0;

        if (trimHead && 0 < d && ' ' == buf[0]) {
            edit = true;

            start++;
        }

        XMLStringFactory xsf = XMLStringFactoryImpl.getFactory();

        return edit ? xsf.newstr(buf, start, d - start) : this;
    }

    /**
     * Convert a string to a double -- Allowed input is in fixed
     * notation ddd.fff.
     *
     * %OPT% CHECK PERFORMANCE against generating a Java String and
     * converting it to double. The advantage of running in native
     * machine code -- perhaps even microcode, on some systems -- may
     * more than make up for the cost of allocating and discarding the
     * additional object. We need to benchmark this.
     *
     * %OPT% More importantly, we need to decide whether we _care_ about
     * the performance of this operation. Does XString.toDouble constitute
     * any measurable percentage of our typical runtime? I suspect not!
     *
     * @return A double value representation of the string, or return Double.NaN
     * if the string can not be converted.  */
    public double toDouble() {
        if (m_length == 0)
            return Double.NaN;
        int i;
        char c;
        String valueString = fsb().getString(m_start, m_length);

        // The following are permitted in the Double.valueOf, but not by the XPath spec:
        // - a plus sign
        // - The use of e or E to indicate exponents
        // - trailing f, F, d, or D
        // See function comments; not sure if this is slower than actually doing the
        // conversion ourselves (as was before).

        for (i = 0; i < m_length; i++)
            if (!XMLCharacterRecognizer.isWhiteSpace(valueString.charAt(i)))
                break;
        if (i == m_length)
            return Double.NaN;
        if (valueString.charAt(i) == '-')
            i++;
        for (; i < m_length; i++) {
            c = valueString.charAt(i);
            if (c != '.' && (c < '0' || c > '9'))
                break;
        }
        for (; i < m_length; i++)
            if (!XMLCharacterRecognizer.isWhiteSpace(valueString.charAt(i)))
                break;
        if (i != m_length)
            return Double.NaN;

        try {
            return Double.parseDouble(valueString);
        } catch (NumberFormatException nfe) {
            // This should catch double periods, empty strings.
            return Double.NaN;
        }
    }
}
